1. Field of the Invention
The present invention relates to an antenna and particularly to an omnidirectional wireless LAN antenna and a cost-effective method for producing the same.
2. Description of the Prior Art
An antenna is used for wireless radio frequency communications, including wireless local loop (WLL) services, cellular mobile radiotelephone (CMR) services, and personal communications services (PCS). An omnidirectional radio frequency antenna is commonly used at the central site for providing communication links between a central fixed site and multiple remote sites. Typically, the antenna is one half or one quarter of a wavelength in length along at least one axis and as such cannot easily be reduced.
One type of a low-profile antenna is an Inverted-F Antenna (IFA) as shown in FIG. 1. A radiating portion 122 is connected to the end of the vertical element 124 of an inverted-L Antenna 12. A signal transmission line 16 is soldered to the radiating portion 122 for signal transmission between the antenna 12 and a communication host. The appearance of the antenna is like a letter F facing the ground plane 14.
However, the conventional method for manufacturing an IFA antenna has difficulties in keeping the RF characteristics stable due to the antenna structure and the poor error tolerance in the manufacture process. For instance, the soldering of the signal transmission line 16 may easily cause a frequency drift.
For optimal transmission and reception of electromagnetic signals, it is desirable to provide an improved antenna structure and the method for producing such an antenna which can keep the RF characteristics stable.
Moreover, the conventional method for manufacturing such an antenna is not efficient enough. It is desirable to provide an antenna with an improved structure to overcome the problems of the prior arts, thereby to increase the yield rate in mass production.
It is a primary object of the present invention to provide an improved structure for an Inverted-F antenna which is compact, cost-effective and environmentally robust.
It is another object of the present invention to provide a method for manufacturing an omnidirectional Inverted-F antenna which can easily keep the RF characteristics of the inverted-F antenna stable.
According to an aspect of the invention, the invention provides an improved structure of the antenna. The improved structure includes: a radiating portion forming a longitudinal side of the Inverted-F antenna, a support portion perpendicularly connected to the radiating portion, a feed-in portion integrally forming a center extending portion of the Inverted-F antenna and a signal transmission line connected to the feed-in portion and the ground plane for signal transmission between the antenna and a communication host. The ground plane, the support portion, and the radiating porting are integrally formed. The signal transmission line includes a core wire and a ground wire. The core wire is connected to the feed-in portion and the ground wire connected to the ground plane.
According to another aspect of the invention, the invention provides a method for manufacturing an antenna. The method includes the steps of: (a). Form a rectangular pattern and an Inverted-F pattern facing the rectangular pattern on a uniform conductor plane by punching. The Inverted-F pattern includes a radiating portion, a support portion, and a feed-in portion. The bottom end of the support portion is connected to the rectangular pattern. (b). Bend the support portion to a horizontal plane perpendicular to the rectangular pattern. And (c). Solder a core wire of a signal transmission line to the radiating portion and a ground wire of a signal transmission line to the ground plane.